Synthetic polymers are widely used in biomedical applications as well as in other articles that come into contact with human skin or tissues, including clothing. Polymers frequently used in biomedical applications include acrylics, polyurethanes, silicones and various hydrophilics. In the area of optical lenses, including intraocular and contact lenses, typically used polymers are polymethylmethacrylate, polyphenylethyl methacrylate, cellulose acetate butyrate, silicone-methylmethacrylate co-polymers, methylmethacrylate co-polymers with hydrophilic compounds, as well as hydrogels such as those based on hydroxyethylmethacrylate and dihydroxypropylmethacrylate. Silicone-containing hydrogels have been prepared by co-polymerization of silicone monomers such as methacryloxy propyl tris(tri-methylsiloxy)silane (TRIS) and/or siloxane macromere, and hydrophilic monomers such as N,N-dimethylacrylamide, N-vinyl pyrrolidone, N-carboxyvinyl ester, etc. Common to these materials is that they provide for surfaces that are very different from known biological surfaces and therefore exhibit various degrees of tissue or bio-incompatibility. Incorporation of amino acids into polymers intended for contact with biological surfaces may enhance their biocompatibility. Bawa described polymers including amino acids in U.S. Pat. No. 4,668,506. However, because the amino acids contained in the polymers of Bawa lack free alpha-amino-carboxy groups, they do not significantly improve the biocompatibility of polymers. Hitz et al. described in international publication WO 2006126095 polymers resulting from co-polymerization of side chain-active acrylic amino acids and conventional acrylic monomers. These polymers that contain amino acids with free alpha-amino-carboxy groups were shown to have a dramatically increased biocompatibility when compared to prior art polymers. Because the amino acids residues incorporated in the polymers are not linked via peptidic bonds, the polymers are resistant to biological degradation by tissue proteases and may give rise to reduced hematological responses. Furthermore, the presence of amino acid residues in the polymers increases their hydrophilicity. Depending on the nature of a polymer, this may translate into enhanced uptake of water, oxygen permeability and surface wetting.
The present invention relates to a novel method for preparing polymers of related character. The method is far simpler and economically more feasible than the methods described in publication WO 2006126095. Furthermore, existing manufacturing procedures for hard lenses as well as hydrogel lenses can be adapted with minimal effort and cost for the production of products containing the new, biocompatible polymers. Chemically, the polymers of the subject invention are related with but are not identical with the closest prior art polymers. The polymers of the present invention contain 2,3-linked (substituted or unsubstituted) succinyl-epsilon-lysinylamide monomers, whereas the closest prior art polymers include 1,2-linked, 2-methylated or unsubstituted, propionyl-epsilon-lysinylamide monomers. On a functional level, the new polymers contain extra negative charges at neutral pH, which charges may play an important biological function in reducing interactions with proteins and other negatively charged molecules present on the biological surface with which the polymers come into contact.